Most reviews will tell you this already, but here's the general idea with Legacy thread.
This thread is definitely the strongest of the invisible threads out on the market. Period. You
will be amazed at how much tension you can put on it and not have it break.
It's also
thicker. Obviously, some of that great strength must come from somewhere, and the thickness does
reveal it. While still thinner than hair, it's thicker than mesika elastics (which regular loops are
made of). Nonetheless, it's quite invisible in darker conditions, and you only need to avoid direct
light when using it. Even then, it's hard to notice unless you're looking directly for it.
It's great for making loops, and much cheaper than buying premade ones. Plus, once again, these
loops are stronger.
So in the end, when you're deciding on what thread to get, it really
depends on your style. If you think you can manage with breaking loops often, or if you can handle
loops well enough that you don't think the extra strength would be useful, then this isn't really
for you. The other ones are less visible anyways. But I'm telling you now, that extra strength is
pretty useful, and the visibility only changes slightly.